Wobble plate-type variable displacement compressor

ABSTRACT

Disclosed is a wobble plate type variable displacement compressor that uses a constant velocity universal joint mechanism, which comprises an inner ring and an outer ring, balls that are held between guide grooves of the inner ring and the outer ring to transmit power, wherein a wobble plate is connected and fixed to the outer ring. In the compressor, the wobble plate is provided with a cylindrical part which extends in the axial direction of a swash plate, and in the relative rotation structure between the swash plate, and the wobble plate and the outer ring, the swash plate is supported to be able to relatively rotate only in relation to the wobble plate via a bearing interposed at least between the cylindrical part and the inner diameter portion of the swash plate, without being supported to be able to rotate relative to the outer ring. With this wobble plate type variable displacement compressor using the specified constant velocity universal joint mechanism, the relative rotation structure between the wobble plate and the outer ring, and the swash plate, can be improved, workability and productivity can be improved, and the cost and weight can be reduced.

RELATED APPLICATIONS

This is a U.S. National Phase Application under 35 USC §371 ofInternational Application PCT/JP2009/058905 filed on May 13, 2009.

This application claims the priority of Japanese Patent Application No.2008-144527 filed Jun. 2, 2008, the entire content of which is herebyincorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a wobble plate type variabledisplacement compressor, and specifically, to a wobble plate typevariable displacement compressor which incorporates therein a newrotation preventing mechanism for the wobble plate.

BACKGROUND ART OF THE INVENTION

A wobble plate type variable displacement compressor is known wherein arotational movement of a swash plate rotated together with a rotationalmain shaft and supported changeably in angle relative to the main shaftis converted into a wobble movement of a wobble plate, and bytransmitting the wobble movement to a piston connected to the wobbleplate, the piston is reciprocated. In such a wobble plate type variabledisplacement compressor, because it is necessary to prevent the rotationof the wobble plate connected to the piston, a rotation preventingmechanism of the wobble plate is incorporated. With respect to therotation preventing mechanism of the wobble plate, various improvementsfor making the compressor small, improving the durability and the silentperformance, facilitating processing, cost down, etc., have beeninvestigated.

For example, in Patent documents 1, 3 and 4, a structure provided with aBirfield type constant velocity universal joint as a wobble platerotation preventing mechanism is disclosed. In this structure, sincewobble parts and a swash plate are supported by an outer ring of aBirfield type constant velocity universal joint provided as a wobbleplate rotation preventing mechanism, and ultimately supported by a mainshaft via a cage of an internal part of the constant velocity universaljoint (a cage for regulating positions of a plurality of balls forperforming power transmission), and further, via an inner ring of theconstant velocity universal joint, the number of interposed partsincreases and the accumulated play becomes great, and therefore, thereis a problem insufficient in vibration, noise and durability.

Further, although the Birfield type constant velocity universal jointdisclosed in Patent documents 1, 3 and 4 theoretically has a structureperforming a rotational power transmission between inner and outer ringsby a plurality of balls, actually it is difficult to achieve uniform andcontinuous contact of the plurality of balls, and therefore, a contactpressure of specified balls may locally increase. Further, because therotational power transmission between inner and outer rings is performedin the shear direction of balls by ball guide grooves formed on each ofinner and outer rings on both sides of a cage, the contact surfacebetween the balls and the guide grooves may have a large inclinationrelative to the power transmission direction. By this, when apredetermined power is transmitted, the contact load generated as avertical reaction force becomes high. Therefore, in order to ensure asufficient transmission ability, it is necessary to employ asufficiently large ball size (ball diameter), and from these reasons, itis difficult to make the structure further small-sized, and it isdifficult to apply it to a small displacement compressor.

Further, since the support for the rotational main shaft of thecompressor in the internal mechanism described in Patent documents 2, 3and 4 is provided on one side relative to the main mechanism portion (acantilever supporting is employed), whirling of the main shaft becomesgreat, and it is disadvantageous on durability, vibration and noise.

Further, in the compression mechanism disclosed in Patent documents 3and 4, since the inner ring of the constant velocity universal joint issupported slidably in the axial direction at a condition being preventedwith rotation, it is necessary to make the main shaft thick in order toensure the rigidity of the main shaft provided to the housing to besufficiently great, and it may cause increase of the weight of the mainshaft and the weight of the product.

Further, in the constant velocity universal joint mechanism disclosed inPatent documents 3 and 4, machining of grooves for regulating thepositions of a plurality of balls operating for power transmission iscomplicated, and the mechanism may be disadvantageous on cost.

Furthermore, in the compression mechanism disclosed in Patent document2, since there is no support in the radial direction due to the mainshaft in the main mechanism portion and play in the wobble portion inthe radial direction tends to become great, by this play, problems ondurability, vibration and noise may occur.

PRIOR ART DOCUMENTS Patent Documents

-   Patent document 1: U.S. Pat. No. 5,112,197-   Patent document 2: U.S. Pat. No. 5,509,346-   Patent document 3: U.S. Pat. No. 5,129,752-   Patent document 4: JP-A-2006-200405

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Paying attention to the problems in the above-described conventionaltechnologies, a wobble plate type variable displacement compressor ispreviously proposed by the applicant of the present invention which usesa constant velocity universal joint small-sized, good in durability andsilent performance, easy-to-machine and inexpensive, that has achievedto realize uniform and continuous contact of a plurality of ballsoperating for power transmission while suppressing play in the radialdirection and rotational direction of the inside of the constantvelocity universal joint provided as a wobble plate rotation preventingmechanism (Japanese Patent Application No. 2006-327988).

In this proposal, as the rotation preventing mechanism of the wobbleplate, a mechanism is provided, which comprises (a) an inner ringprovided in a housing movably in an axial direction although rotation isprevented, supporting a rotational main shaft via a bearing at an innerdiameter portion to rotate relatively and to move relatively in an axialdirection and having a plurality of guide grooves for guiding aplurality of balls provided for power transmission, (b) a sleevefunctioning as a wobble central member of the wobble movement of thewobble plate, provided on the rotational main shaft to rotate relativelythereto and to move in an axial direction and engaged with the innerring movably in an axial direction together with the inner ring, (c) anouter ring having a plurality of guide grooves for guiding the balls atpositions opposing respective guide grooves of the inner ring, supportedon the sleeve wabblingly, supporting the wobble plate fixedly on anouter circumference and supporting the swash plate rotatably via abearing, and (d) a plurality of balls held by the guide grooves formedin the inner ring and the outer ring at a condition of opposing eachother and performing power transmission by being compressed between theguide grooves.

By this proposal, a wobble plate type variable displacement compressormade small-sized, good in durability and silent performance,easy-to-machine and inexpensive, has become possible, but, even in thisproposed mechanism, matters to be further improved are still left.Namely, in the above-described previous proposal, the wobble plate andthe outer ring in the wobble plate rotation preventing mechanism areformed as a wobble portion which can rotate relative to the swash plateand the rotation of which itself is prevented, and this relativerotation structure relative to the swash plate is formed via a bearinginterposed between the wobble plate and the swash plate and a bearinginterposed between the outer ring and the swash plate. More concretely,an annular portion forming an outer circumferential cylindrical surfaceof the outer ring of the rotation preventing mechanism is extended inthe axial direction up to the inside of the swash plate, and the outercircumferential cylindrical surface is supported in the swash plate viaa bearing so as to be able to rotate relative to the swash plate.However, although the annular portion of the outer ring of the rotationpreventing mechanism must be made thin from restriction in outerdiameter dimension, it is difficult to make the part of the thin andlong annular portion, and after the annular portion is made as a thickportion, it is made thin by machine processing, and therefore, theworkability and productivity are not good and increase of cost iscaused. Further, because an iron based material is used for the outerring of the rotation preventing mechanism relative to the wobble platemade from an aluminum based material, increase of weight is causedaccompanying with increase of the length in the axial direction.

Accordingly, paying attention to the problems left in theabove-described new wobble plate rotation preventing mechanism using aspecified constant velocity universal joint mechanism which waspreviously proposed by the applicant of the present invention, an objectof the present invention is to provide a wobble plate type variabledisplacement compressor which can improve the relative rotationstructure between the above-described wobble plate and the outer ring inthe rotation preventing mechanism, and the swash plate, therebyimproving the workability and productivity and reducing the cost andweight.

Means for Solving the Problems

To achieve the above-described objects, a wobble plate type variabledisplacement compressor according to the present invention has pistonsinserted reciprocally into cylinder bores, a swash plate rotatedtogether with a rotational main shaft and supported changeably in anglerelative to the main shaft, a wobble plate which is connected to thepistons, in which a rotational movement of the swash plate is convertedinto a wobble movement of the wobble plate, and which transmits thewobble movement to the pistons to reciprocate the pistons, and arotation preventing mechanism of the wobble plate, and is characterizedin that

the rotation preventing mechanism of the wobble plate comprises (a) aninner ring provided in a housing movably in an axial direction whilebeing prevented with rotation and having a plurality of guide groovesfor guiding a plurality of balls provided for power transmission, (b) anouter ring having a plurality of guide grooves for guiding the balls atpositions opposing respective guide grooves of the inner ring, andconnected with the wobble plate on an outer circumference of the outerring and supported wobblingly together with the wobble plate, and (c) aplurality of balls held by the guide grooves formed in the inner ringand the outer ring at a condition of opposing each other and performingpower transmission by being compressed between the guide grooves, and

the wobble plate connected to the outer ring is provided with acylindrical part which extends in an axial direction of the swash plate,and in a relative rotation structure between the swash plate, and thewobble plate and the outer ring, the swash plate is supported to be ableto relatively rotate only in relation to the wobble plate via a bearinginterposed at least between the cylindrical part and an inner diameterportion of the swash plate, without being supported to be able to rotaterelative to the outer ring. Where, the inner ring can support therotational main shaft at its inner diameter portion, so that the mainshaft can rotate relatively and can move relatively in the axialdirection.

In the rotation preventing mechanism of the wobble plate thusconstructed, first, the outer ring of the rotation preventing mechanismis supported wobblingly together with the wobble plate, and the wobbleplate rotation preventing mechanism is formed via the guide groovesopposing each other, formed on the inner and outer rings, and the ballsheld between the guide grooves. Then, the inner ring is supported in thehousing movably in the axial direction and prevented with rotation, andby the inner diameter portion of this inner ring, for example, by thebearing provided in the inner diameter portion, the rotational mainshaft, for example, the rear end portion of the rotational main shaft,is supported. Therefore, the rotational main shaft is rotatablysupported at both sides of the compression main mechanism portion (thatis, inboard type supporting), a sufficiently high rigidity can be easilyensured, the whirling of the main shaft may be suppressed small, andtherefore, it becomes possible to make the diameter of the main shaftsmall, improve the reliability and reduce vibration and noise. Further,because the whirling of the main shaft is suppressed, the deflection ofthe swash plate rotated together with the main shaft may be suppressedsmall, and the rotational balance of the whole of the rotational portionmay be improved. Further, by optimizing the formation of the guidegrooves formed on the inner ring and the outer ring which oppose eachother, uniform and continuous contact of the balls held between theguide grooves becomes possible, and therefore, it becomes possible toimprove the reliability and reduce vibration and noise. Furthermore, theguide grooves of balls may be formed so that balls can roll between apair of guide grooves separated from each other accompanying with themovement of the intersection of both guide grooves, complicated shapesare not required for the guide grooves themselves, and therefore, themachining therefor is facilitated and becomes advantageous on cost. Insuch a structure according to the present invention, basically, theplurality of balls operating for power transmission perform powertransmission at a condition where they are nipped and supported betweenguide grooves facing to each other in the compression direction. Bythis, an actual contact area can be ensured sufficiently large, itbecomes possible to reduce the contact surface pressure, and it becomesadvantageous on reliability. Further, because the contact surfacepressure can be reduced, it becomes possible to make the diameter ofballs small and it becomes also possible to make the whole of therotation preventing mechanism small-sized.

Then, with respect to the above-described wobble plate rotationpreventing mechanism, the relative rotation structure between the swashplate, and the wobble plate and the outer ring, is improved as follows,as compared with the case of being formed by interposing bearings bothof between the swash plate and the wobble plate and between the swashplate and the outer ring as in the previous proposal. Namely, acylindrical part extending in the axial direction of the swash plate isprovided to the wobble plate connected to the outer ring, and in therelative rotation structure between the swash plate, and the wobbleplate and the outer ring, the swash plate is supported to be able torelatively rotate only in relation to the wobble plate via a bearinginterposed at least between the above-described cylindrical part and aninner diameter portion of the swash plate, without being supported to beable to rotate relative to the outer ring. By this structure, the axiallength of the outer circumferential annular portion of the outer ring,which has been extended up to the inner diameter portion of the swashplate, can be greatly shortened, and the problems of deterioration ofworkability and productivity and increase of cost, that have been causedfor making the annular portion thin, can be solved. Further, since thewhole of the outer ring can be made small, the weight of the outer ringmade of an iron-based material can be greatly reduced. Instead, althougha cylindrical part extending in the axial direction of the swash plateis to be provided to the wobble plate in order to achieve the relativerotation structure between the wobble plate and the swash plate, becausethe wobble plate can be formed from an aluminum-based material, bymaking the outer ring small-sized as described above, an advantage forreducing the weight relative to the whole of the wobble plate rotationpreventing mechanism can be surely obtained. Where, because the wobbleplate is formed as a larger-diameter member as compared with the outerring, the difficulty in forming and the difficulty in machining forforming of the annular portion of the outer ring, that have beenrequired to be made thin in the previous proposal, are not accompanied,and therefore, it is possible to manufacture a wobble plate having adesirable shape relatively easily.

In this wobble plate type variable displacement compressor, a structuremay be employed wherein the inner ring in the above-described wobbleplate rotation preventing mechanism slides directly on the rotationalmain shaft in the axial direction, and a structure may also be employedwherein the inner ring slides via a sleeve. In the latter case, astructure may be employed wherein the above-described wobble platerotation preventing mechanism further comprises (d) a sleeve functioningas a wobble central member of the wobble movement of the wobble plate,provided on the rotational main shaft to rotate relatively thereto andto move in the axial direction and engaged with the inner ring movablyin the axial direction together with the inner ring, and theabove-described outer ring is supported wobblingly on the sleeve.

In such a wobble plate type variable displacement compressor accordingto the present invention, a structure may be employed wherein the guidegrooves opposing each other of the inner ring and the outer ring of theabove-described wobble plate rotation preventing mechanism are formed ata relative angle of 30 to 60 degrees relative to a center axis of therotational main shaft, and guide grooves opposing each other for forminga single ball guide are disposed so as to be symmetric relative to aplane perpendicular to the main shaft and passing through a wobblecenter of the wobble plate at a condition where a relative angle betweenan axis of the inner ring and an axis of the outer ring is zero. By thestructure where the guide grooves opposing each other are disposed at acrossed axes angle within a predetermined range and both guide groovesformed in the directions crossed with each other are disposedsymmetrically relative to the plane passing through the wobble center ofthe wobble plate, it becomes possible that the balls held between theguide grooves are brought into contact with both guide grooves at auniform and continuous condition, the vibration and noise at thisportion may be greatly reduced, and the reliability may be greatlyimproved.

Further, in this constitution, a structure may be employed wherein twoball guides adjacent to each other among a plurality of ball guides ofthe above-described rotation preventing mechanism are referred to be apair of ball guides, and the pair of ball guides are disposed inparallel to each other. By such a structure, because the play in therotational direction in the rotation preventing mechanism portion isschematically decided by a relationship between the distance between thebottoms of the pair of guide grooves provided, on the inner and outerrings and the diameter of the balls, setting and management of an actualclearance between the bottoms of the guide grooves and the balls arefacilitated, and it becomes possible to suppress the play to be small bysetting a proper clearance.

In this constitution, a structure may be employed wherein the pair ofball guides disposed in parallel to each other are disposedsymmetrically relative to a plane including a center axis of therotational main shaft, and a structure also may be employed wherein aguide groove forming one ball guide of the pair of ball guides, whichare disposed in parallel to each other, is disposed so that its axis ispositioned on a plane including a center axis of the rotational mainshaft. In the former structure, a rotation preventing mechanism, inwhich a rotational direction may not be selected, can be formed, and itbecomes possible to reduce the contact load of the balls, and in thelatter structure, it becomes possible to further reduce the contact loadby setting the power transmission direction at a specified direction.

Further, in the above-described wobble plate rotation preventingmechanism, a structure may be employed wherein two ball guides disposedon both sides of the rotational main shaft approximately symmetricallyrelative to the rotational main shaft among the plurality of ball guidesare referred to be a pair of ball guides, and the pair of ball guidesare disposed in parallel to each other. By this structure, because theplay in the rotational direction in the rotation preventing mechanismportion is schematically decided by a relationship between the distancebetween the bottoms of the pair of guide grooves provided on the innerand outer rings and the diameter of the balls, it becomes possible toset and manage actual clearances in both ball guides simultaneously atdesirable clearances, by disposing two ball guides symmetricallydisposed in parallel to each other. As a result, the setting andmanagement of the clearances are facilitated, and it becomes possible tosuppress the play to be small.

In this structure, it is preferred that the above-described pair of ballguides, which are disposed in parallel to each other, are disposed sothat axes of guide grooves forming the pair of ball guides arepositioned on a plane including a center axis of the rotational mainshaft. By disposing the pair of ball guides on the plane including thecenter axis of the rotational main shaft, it becomes possible tominimize the ball contact load without selecting the power transmissiondirection.

Effect According to the Invention

Thus, in the wobble plate type variable displacement compressoraccording to the present invention, as compared with the wobble platerotation preventing mechanism using the conventional constant velocityuniversal joint, uniform and continuous contact of a plurality of ballsoperating for power transmission can be achieved while the play can besuppressed small, a rotation preventing mechanism small-sized, excellentin durability and silent performance, good in rotational balance, easyin machining and inexpensive can be realized, and a wobble plate typevariable displacement compressor, having an excellent performance whichhas not been achieved by the conventional technologies, can be provided.And, in the wobble plate rotation preventing mechanism of thiscompressor, since a structure is employed wherein a cylindrical partextending in the axial direction of the swash plate is provided to thewobble plate, and the swash plate is supported to be able to relativelyrotate only in relation to the wobble plate without being supported tobe able to rotate relative to the outer ring, the problems ofdeterioration of workability and productivity of the outer ring andincrease of cost in the previous proposal can be solved, and the weightof the entire mechanism can be reduced by forming the whole of the outerring small. Therefore, improvement of workability and productivity andreduction of cost and weight, that are objects in the present invention,can be surely achieved.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a compressor showing an exampleof a basic structure of a wobble plate type variable displacementcompressor having a wobble plate rotation preventing mechanism in thepresent invention.

FIG. 2 is a vertical sectional view of the wobble plate type variabledisplacement compressor depicted in FIG. 1, showing an operationalcondition different from that depicted in FIG. 1.

FIG. 3 is an exploded perspective view of a main portion including awobble plate rotation preventing mechanism of the wobble plate typevariable displacement compressor depicted in FIG. 1.

FIG. 4 shows an example of the structure of the wobble plate typevariable displacement compressor depicted in FIG. 1, FIG. 4 (A) is apartial, vertical sectional view thereof, and FIG. 4 (B) is a partialelevational view thereof.

FIG. 5 is a partial elevational view showing another example of thestructure of the wobble plate type variable displacement compressordepicted in FIG. 1.

FIG. 6 is a vertical sectional view of a wobble plate type variabledisplacement compressor in which a relative rotation structure between awobble plate and an outer ring, and a swash plate, is improved, ascompared with the structure in the wobble plate type variabledisplacement compressor depicted in FIG. 1.

FIG. 7 is an exploded perspective view of a main portion including thewobble plate rotation preventing mechanism of the wobble plate typevariable displacement compressor depicted in FIG. 6.

FIG. 8 (A) is a partial vertical sectional view showing the relativerotation structure between a wobble plate and an outer ring, and a swashplate, in the compressor depicted in FIG. 1, and FIG. 8 (B) is a partialvertical sectional view showing the relative rotation structure betweenthe wobble plate and the outer ring, and the swash plate, in thecompressor depicted in FIG. 6.

FIG. 9 is a partial elevational view showing a further example of thestructure of the wobble plate type variable displacement compressordepicted in FIG. 1.

FIG. 10 shows partial elevational views showing further examples of thestructure of the wobble plate type variable displacement compressordepicted in FIG. 1, and FIG. 10 (A) and FIG. 10 (B) show examplesdifferent from each other.

FIG. 11 is a partial elevational view showing a still further example ofthe structure of the wobble plate type variable displacement compressordepicted in FIG. 1.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be explainedreferring to figures.

First, in order to understand a new wobble plate rotation preventingmechanism in a wobble plate type variable displacement compressoraccording to the present invention, an embodiment of the basic structureof the whole of this wobble plate type variable displacement compressorwill be explained referring to FIGS. 1-5, and next, for the embodimentof this basic structure, with respect to a structure improved by thepresent invention, in particular, a structure wherein an outer ring ismade small-sized and a swash plate is supported only by the wobble plateside so as to be able to relatively rotate, FIGS. 6-8 will be explained.

FIG. 1 shows an example of a basic structure of the whole of a wobbleplate type variable displacement compressor having a wobble platerotation preventing mechanism according to the present invention, andshows its entire structure in the operation state at the condition ofthe displacement achieving its maximum discharge. FIG. 2 shows theoperation state of the wobble plate type variable displacementcompressor depicted in FIG. 1 at the condition of the displacementachieving its minimum discharge. FIG. 3 shows a main portion including awobble plate rotation preventing mechanism in the wobble plate typevariable displacement compressor according to the embodiment of thebasic structure depicted in FIG. 1, as an exploded perspective view.

In FIGS. 1 and 2, a wobble plate type variable displacement compressor 1has a housing 2 disposed at the central portion, a front housing 3 and arear housing 4 disposed on both sides of the housing 1 as its housings,and a rotational main shaft 5 inputted with a rotational drive powerfrom outside is provided over the range from the portion of housing 2 upto the position extending through front housing 3. A rotor 6 is fixed torotational main shaft 5 so as to be rotated integrally with main shaft5, and a swash plate 8 is connected to rotor 6 via a hinge mechanism 7,changeably in angle and rotatably together with rotational main shaft 5.Piston 10 is reciprocally inserted into each cylinder bore 9, and piston10 is connected to wobble plate 12 via connecting rod 11. The rotationalmovement of swash plate 8 is converted into the wobble movement ofwobble plate 12, the wobble movement is transmitted to piston 10 viaconnecting rod 11, and piston 10 is reciprocated. Fluid to be compressed(for example, refrigerant) is sucked from suction chamber 13 formed inrear housing 4 into cylinder bore 9 through suction hole 15 formed onvalve plate 14 (a suction valve is omitted in the figure) accompanyingwith the reciprocating movement of piston 10, and after the sucked fluidis compressed, the compressed fluid is discharged into discharge chamber17 through discharge hole 16 (a discharge valve is omitted in thefigure), and therefrom, sent to an external circuit.

It is necessary that the above-described wobble plate 12 performs awobble movement at a condition where its rotation is prevented.Hereinafter, the remaining portions of compressor 1 will be explainedmainly with respect to the rotation preventing mechanism of this wobbleplate 12, referring to FIGS. 1 to 3.

Rotation preventing mechanism 21 of wobble plate 12 is formed from amechanism comprising (a) an inner ring 27 provided in housing 2 movablyin the axial direction although its rotation is prevented, supportingrotational main shaft 5 via a bearing 22 (radial bearing) at its innerdiameter portion to rotate relatively and to move relatively in theaxial direction and having a plurality of guide grooves 26 for guiding aplurality of balls 25 provided for power transmission, (d) a sleeve 24functioning as a wobble central member of the wobble movement of wobbleplate 12, provided on rotational main shaft 5 to rotate relativelythereto and to move in the axial direction and engaged with inner ring27 movably in the axial direction together with inner ring 27, (b) anouter ring 30 having a plurality of guide grooves 28 for guiding balls25 at positions opposing respective guide grooves 26 of inner ring 27,supported on sleeve 24 wabblingly, connected with wobble plate 12fixedly on its outer circumference and supporting swash plate 8rotatably via a bearing 29 (radial bearing), and (c) a plurality ofballs 25 held by guide grooves 26, 28 formed in inner ring 27 and outerring 30 at a condition of opposing each other and performing powertransmission by being compressed between guide grooves 26, 28. Thrustbearings 31, 32 are interposed between wobble plate 12 and swash plate 8and between rotor 6 and front housing 3, respectively. Further, althoughinner ring 27 is supported in housing 9 movably in the axial direction,its rotation is prevented. As means for preventing the rotation, ageneral rotation regulating means such as a key or a spline may be used(not depicted). Furthermore, although the rear end of rotational mainshaft 5 is supported by bearing 22 provided on the inner diameterportion of inner ring 27, because rotational main shaft 5 is supportedalso at the side of front housing 3 through the compression mainmechanism portion rotatably via bearing 33 (radial bearing), it isradially supported on both sides (inboard supporting).

In rotation preventing mechanism 21 of wobble plate 12 constructed asdescribed above, outer ring 30 is wabblingly supported by sleeve 24through the spherical surface contact, and sleeve 24 is supported byrotational main shaft 5 rotatably and movably in the axial direction,and by this structure, it is possible to make play in the radialdirection between rotational main shaft 5 and the whole of the wobblemechanism portion small, thereby improving the reliability and reducingvibration and noise.

Further, in the above-described embodiment, since rotational main shaft5 is supported in the condition of inboard supporting on both sides ofthe compression main mechanism portion by bearing 22 provided in theinner diameter portion of inner ring 27 and bearing 33 provided on fronthousing 3 side, a sufficiently high rigidity can be ensured even if thediameter of main shaft 5 is relatively small, the whirling of main shaft5 can also be suppressed, making small-sized can be easily achieved, andimprovement of reliability and reduction of vibration and noise may bepossible. Further, as the result of suppressing the whirling ofrotational main shaft 5, the whole of the rotational portion rotatedtogether with rotational main shaft 5 can be suppressed to be small, andtherefore, the rotational balance of the whole of the rotated portionbecomes remarkably good. Where, in the above-described structure, it ispossible to extend rotational main shaft 5 rearward and to replace itfor a structure being supported directly by housing 2 via a bearing.

Moreover, in the above-described embodiment, by the engagement of thespherical surface (concave spherical surface) formed in the innerdiameter side of inner ring 27 with the spherical surface (convexspherical surface) formed in the outer diameter side of sleeve 24, amutual supporting between both members is performed. By adjusting aclearance in this supporting portion, it is possible to absorb arelative whirling of the inner and outer rings caused by the dispersionof the positions of the guide grooves for a plurality of balls operatingfor power transmission, whereby the uniform and continuous contact ofballs 25 is further improved, and it is more advantageous with respectto reliability, vibration and noise.

FIG. 4 shows a condition where the relative angle between the inner andouter rings is zero in rotation preventing mechanism 21 of wobble plate12. As depicted in FIG. 4(A), guide grooves 26, 28 formed on inner ring27 and outer ring 24 of rotation preventing mechanism 21 are disposed atrelative angles (relative angles within a range of 30 to 60 degrees)relative to the center axis of rotational main shaft 5. Guide groove 26formed on inner ring 27 (the axis of guide groove 26 is indicated bysymbol 42) and guide groove 28 formed on outer ring 30 (the axis ofguide groove 28 is indicated by symbol 43), which form one ball guide 41and oppose each other, are disposed so as to be symmetric relative toplane 44 which is perpendicular to rotational main shaft 5 and passesthrough the wobble center of wobble plate 12, at a condition where therelative angle between the axis of inner ring 27 and the axis of outerring 30 is zero. Ball 25 is regulated and supported on the intersectionof axis 42 of guide groove 26 and axis 43 of guide groove 28. Further,as depicted in FIG. 4(B), a structure can be employed wherein two ballguides adjacent to each other among a plurality of ball guides 41 ofrotation preventing mechanism 21 are referred to be a pair of ballguides, and respective ball guides 41 in the pair of ball guides 45, inother words, axes 46 of the guide grooves formed on the inner and outerrings in this portion, are disposed in parallel to each other. In such astructure, as aforementioned, because the play in the rotationaldirection in the rotation preventing mechanism portion is schematicallydecided by a relationship between the distance between the bottoms ofthe pair of guide grooves provided on the inner and outer rings and thediameter of the balls, setting and management of an actual clearance arefacilitated, and it becomes possible to suppress the play to be small bysetting a proper clearance. A plurality of balls 25 operating for powertransmission are supported in the compression direction between guidegrooves 26, 28 facing each other through the respective balls, andperform power transmission. Since ball 25 is held by guide grooves 26,28 facing each other so as to be embraced and come into contact withboth guide grooves 26, 28, the contact area between ball and therespective guide grooves 26, 28 may be ensured to be sufficient large,it becomes possible to reduce the contact surface pressure, and astructure remarkably advantageous in reliability, vibration and silentperformance may be realized. Further, it is also possible to make thediameter of balls 25 small, and the whole of the rotation preventingmechanism may be made small.

Further, the load applied to ball, which is provided as a moment whosecenter is rotational main shaft 5, is generated as a perpendicularreaction force of the actual contact surface. The smaller theinclination of the normal line of the contact surface relative to thedirection of the moment is, the smaller the contact load becomes, and asdepicted in FIG. 5, by a structure where the pair of ball guides 45disposed in parallel as described above are disposed symmetricallyrelative to plane 47 including center axis 5 a of rotational main shaft5, in other words, by a structure where axes 46 of two sets of guidegrooves formed on the inner and outer rings are disposed symmetricallyrelative to plane 47 including center axis 5 a of rotational main shaft5, the mechanism is made as a rotation preventing mechanism which doesnot select the rotational direction, and it is possible to minimize theball contact load.

In the present invention, as compared with the above-described exampleof the basic structure, a relative rotation structure between swashplate 8, and wobble plate 12 and outer ring 30, is improved, forexample, as shown in FIGS. 6 to 8. Where, in a wobble plate typevariable displacement compressor 1 a having an improved structure shownin FIGS. 6 to 8, because the portions other than an outer ring 30 a anda wobble plate 12 a are basically same as the structure shown in FIGS. 1to 3, the explanation for the same portions will be omitted by providingthe same symbols to the same portions as the symbols provided in FIGS. 1to 3.

As shown in FIGS. 6 and 7, a cylindrical part 51 extending in swashplate 8 in the axial direction of swash plate 8 is provided to wobbleplate 12 a connected to outer ring 30 a, and swash plate 8 is supportedto be able to relatively rotate only in relation to wobble plate 12 avia a bearing 29 (radial bearing) interposed between the outercircumferential surface of this cylindrical part 51 and the innerdiameter portion of swash plate 8 and a bearing 31 (thrust bearing)interposed between the side surface of wobble plate 12 a and the sidesurface of swash plate 8. Namely, a relative rotation structure isformed between swash plate 8, and wobble plate 12 a and outer ring 30 a,without supporting swash plate 8 relative to outer ring 30 a so as to beable to relatively rotate. In order to show this portion more clearly,FIG. 8 shows a comparison between the structure (FIG. 8 (A)) whereinswash plate 8 is supported to be able to relatively rotate, on the outercircumferential surface of the outer circumferential annular portion ofouter ring 30 shown in FIGS. 1 to 3 via bearing 29, and the structure(FIG. 8 (B)) wherein swash plate 8 is supported to be able to relativelyrotate, on the outer circumferential surface of extended cylindricalpart 51 of wobble plate 12 a via bearing 29 by the improvement accordingto the present invention.

In the present invention, cylindrical part 51 extending in the axialdirection of swash plate 8 is provided to wobble plate 12 a, and swashplate 8 is supported to be able to relatively rotate in relation tocylindrical part 51 of wobble plate 12 a via bearing 29, without beingsupported to be able to rotate relative to outer ring 30 a. With respectto the structure wherein swash plate 8 is supported to be able torelatively rotate in relation to wobble plate 12 a via bearing 31(thrust bearing), there is no substantial difference between FIGS. 8 (A)and (B). By this structure wherein swash plate 8 is supported inrelation to cylindrical part 51 via bearing 29, it becomes unnecessarythat outer ring 30 a extends up to the inner diameter portion of theswash plate, the axial length of annular portion 52 in the structureshown in FIG. 8 (A) can be greatly shortened, and the problems ofdeterioration in workability and productivity and the problem ofincrease in cost having been caused by making this annular portion 52thin can be solved. Further, by making annular portion 52 unnecessary orgreatly shortening it, outer ring 30 a is formed small-sized, andtherefore, the weight of outer ring 30 a made from an iron-basedmaterial can be greatly reduced. Since wobble plate 12 a can be formedfrom an aluminum-based material, even if cylindrical part 51 isprovided, as compared with a case where annular portion 52 of aniron-based material exists, a great advantage for reducing the weightcan be obtained. Therefore, in this section, improvement of workabilityand productivity and reduction of cost and weight can be all achieved.

In the present invention, as an embodiment other than the embodimentdepicted in FIGS. 1-5, for example, as depicted in FIG. 9, by offsettingone ball guide 63 mainly operating in power transmission direction ofouter ring 62 among the pair of ball guides 61, in other words, axis 64of the guide groove in the ball guide 63, onto plane 65 including centeraxis 5 a of rotational main shaft 5, it is possible to further reducethe contact load in the specified restricted power transmissiondirection. Where, in FIG. 9, arrow 66 indicates power transmissiondirection of inner ring.

Further, as shown in FIG. 10 (A) or (B), a structure can also beemployed wherein two ball guides disposed on both sides of rotationalmain shaft 5 approximately symmetrically relative to rotational mainshaft 5 among a plurality of ball guides are referred to be a pair ofball guides, and the pair of ball guides 71 are disposed in parallel toeach other, in other words, axes 72 of guide grooves formed on innerring 27 and outer ring 30 forming the pair of ball guides 71 aredisposed in parallel to each other. By this structure, because the playin the rotational direction in the rotation preventing mechanism portionis schematically decided by a relationship between the distance betweena set of bottoms of the pair of guide grooves provided on inner andouter rings 27, 30 and the diameter of the balls, it becomes possible toset and manage the clearances in both ball guides simultaneously atdesirable clearances, by disposing two ball guides, symmetricallydisposed, in parallel to each other. Consequently, the setting andmanagement of the clearances are facilitated, and it becomes possible tosuppress the play to be small.

Further, in this structure where the pair of ball guides are disposed inparallel to each other, as shown in FIG. 11, a structure can be employedwherein the pair of ball guides 81, which are disposed in parallel toeach other, are disposed so that axes 82 of guide grooves forming thepair of ball guides are positioned on plane 83 including center axis 5 aof rotational main shaft 5. In such a structure, the ball contact loadis minimized without selecting the power transmission direction.

INDUSTRIAL APPLICATIONS OF THE INVENTION

The wobble plate type variable displacement compressor according to thepresent invention can be applied to a wobble plate type variabledisplacement compressor used in any field, and especially, it issuitable for use in the field for vehicles highly requiring makingsmall-sized, increase of reliability, improvement of durability andsilent performance, and cost down, in particular, for use in an airconditioning system for vehicles.

EXPLANATION OF SYMBOLS

-   1, 1 a: wobble plate type variable displacement compressor-   2: housing-   3: front housing-   4: rear housing-   5: rotational main shaft-   5 a: center axis-   6: rotor-   7: hinge mechanism-   8: swash plate-   9: cylinder bore-   10: piston-   11: connecting rod-   12, 12 a: wobble plate-   13: suction chamber-   14: valve plate-   15: suction hole-   16: discharge hole-   17: discharge chamber-   21: rotation preventing mechanism of wobble plate-   22, 23, 29, 33: bearing (radial bearing)-   24: sleeve-   25: ball-   26: guide groove of inner ring-   27: inner ring-   28: guide groove of outer ring-   30, 30 a: outer ring-   31, 32: thrust bearing-   41: ball guide-   42, 43: axis of guide groove-   44: plane passing through wobble center-   45: pair of ball guides-   46: axes of guide grooves formed on inner and outer rings-   47: plane including center axis of rotational main shaft-   51: cylindrical part of wobble plate-   52: annular portion-   61: pair of ball guides-   62: power transmission direction of outer ring-   63: one ball guide-   64: axis of guide groove-   65: plane including center axis of rotational main shaft-   66: power transmission direction of inner ring-   71: pair of ball guides-   72: axis of guide groove-   81: pair of ball guides-   82: axis of guide groove-   83: plane including center axis of rotational main shaft

The invention claimed is:
 1. A wobble plate type variable displacementcompressor having pistons inserted reciprocally into cylinder bores, aswash plate rotated together with a rotational main shaft and supportedchangeably in angle relative to said main shaft, a wobble plate which isconnected to said pistons, in which a rotational movement of said swashplate is converted into a wobble movement of said wobble plate, andwhich transmits said wobble movement to said pistons to reciprocate saidpistons, and a rotation preventing mechanism of said wobble plate,characterized in that said rotation preventing mechanism of said wobbleplate comprises (a) an inner ring provided in a housing movably in anaxial direction while being prevented from rotation relative to thehousing, the inner ring having a plurality of guide grooves for guidinga plurality of balls provided for force transmission, the inner ringbeing configured to move in the axial direction on the main shaft, (b)an outer ring having a plurality of guide grooves for guiding said ballsat positions opposing respective guide grooves of said inner ring, andconnected to said wobble plate on an outer circumference of said outerring and supported wobblingly together with said wobble plate, (c) theplurality of balls being held by said guide grooves formed in said innerring and said outer ring and performing force transmission by being heldbetween said guide grooves which oppose each other, and (d) a sleevefunctioning as a wobble central member of said wobble movement of saidwobble plate, provided on said rotational main shaft to rotaterelatively thereto and to move in an axial direction and engaged withsaid inner ring movably in an axial direction together with said innerring, and said outer ring is supported wobblingly on said sleeve, saidwobble plate is provided with a cylindrical part which extends in theaxial direction and is connected to said outer ring, said swash plate issupported to be able to rotate relative to said wobble plate via abearing interposed at least between said cylindrical part and an innerdiameter portion of said swash plate, and said main shaft is rotatablysupported within the housing, the housing having the cylinder bores at arear end and an inboard support for the main shaft at a front end,wherein said guide grooves opposing each other of said inner ring andsaid outer ring of said wobble plate rotation preventing mechanism areformed at a relative angle of 30 to 60 degrees relative to a center axisof said rotational main shaft, and guide grooves opposing each other forforming a single ball guide are disposed so as to be symmetric relativeto a plane perpendicular to said main shaft and passing through a wobblecenter of said wobble plate at a condition where a relative anglebetween an axis of said inner ring and an axis of said outer ring iszero.
 2. The wobble plate type variable displacement compressoraccording to claim 1, wherein two ball guides adjacent to each otheramong a plurality of ball guides of said wobble plate rotationpreventing mechanism are a pair of ball guides disposed in parallel toeach other.
 3. The wobble plate type variable displacement compressoraccording to claim 2, wherein said pair of ball guides disposed inparallel to each other are disposed symmetrically relative to a planeincluding a center axis of said rotational main shaft.
 4. The wobbleplate type variable displacement compressor according to claim 2,wherein a guide groove forming one ball guide of said pair of ballguides, which are disposed in parallel to each other, is disposed sothat its axis is positioned on a plane including a center axis of saidrotational main shaft.
 5. The wobble plate type variable displacementcompressor according to claim 1, wherein two ball guides disposed onboth sides of said rotational main shaft approximately symmetricallyrelative to said rotational main shaft among a plurality of ball guidesof said wobble plate rotation preventing mechanism are a pair of ballguides disposed in parallel to each other.
 6. The wobble plate typevariable displacement compressor according to claim 5, wherein said pairof ball guides, which are disposed in parallel to each other, aredisposed so that axes of guide grooves forming said pair of ball guidesare positioned on a plane including a center axis of said rotationalmain shaft.
 7. The wobble plate type variable displacement compressoraccording to claim 1, wherein an inner diameter side of the inner ringhas a spherical surface and an outer diameter side of the sleeve has aspherical surface, and the inner ring and the sleeve are mutuallysupported by engaging the spherical surface of the inner diameter sideof the inner ring with the spherical surface of the outer diameter sideof the sleeve so that there is a clearance between the sphericalsurfaces.